By Squadron Leader Zahid Mir CS&IT Department , Superior University PHY-AP -11 Magnetism By Squadron Leader Zahid Mir CS&IT Department , Superior University

Magnets Magnets have been known for centuries. The Chinese and Greeks knew about the “magical” properties of magnets. The ancient Greeks used a stone substance called “magnetite” (an oxide of iron). They discovered that the stone always pointed in the same direction. Later, stones of magnetite called “lodestones” were used in navigation.

William Gilbert, an English physician, first proposed in 1600 that the earth itself is a magnet, and he predicted that the Earth would be found to have magnetic poles.

What is Magnetism? Magnetism is the force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.

Magnetic Needle A magnetized steel rod that, when adjusted to swing in a horizontal plane, indicates the direction of the Earth’s magnetic field. The “RED” end always point towards the geographical north, also known as “North-Seeking Pole”

Magnetic Interactions One magnet set up a magnetic field and the other magnet respond to that magnetic field. Magnet Field Magnet

Magnetic Field of a Bar Magnet

Magnetism First Law Like poles repel each other while unlike poles attract each other.

Magnetic fields due to Current Compass needle indicates the direction of magnetic field around a current carrying wire. Magnetic field vanishes when current is switched off. This shows a direct link between electricity and magnetism